The present invention relates to an actuator of the type comprising, on the one hand, a body and a control element which can be displaced relative to the body, under the control of an actuator motor and, on the other hand, a transducer disposed between the body and the control element, said transducer being designed to provide a raw measurement value representative of the current position of the control element relative to the body.
In order to improve the comfort of the user, many seats are nowadays fitted with electrical actuating devices enabling the configuration of the seat to be modified by displacing moveable elements thereof. In particular, such seats are used especially in transport vehicles such as aircraft, boats and railway carriages.
It is common for every seat to have a reclining back, articulated about one end of a seat-part, as well as a leg rest, articulated about the other end of the seat-part. Both the back and the leg rest can be displaced under the control of an actuating device between a substantially vertical position and a substantially horizontal position, thereby enabling the seat to assume several configurations. For example, these configurations include a configuration in which the user is in a sleeping position, when the back and the leg rest are both substantially horizontal, and a sitting configuration, in which the leg rest and the back are both substantially vertical.
An actuating device is provided so that each moveable element of the seat can be directly and independently controlled.
In addition, many seats are fitted with devices which enable the leg rest and the foot rest to be moved simultaneously by a single command, in order to place the seat in a predetermined configuration with a single command.
For each of these predetermined configurations of the seat, a predetermined target position is fixed for each seat element and hence each actuator.
So that the position of the different seat elements is known at every instant, thereby enabling their displacement to be readily managed, a known approach is to provide in the actuating devices of the seat elements a transducer, such as a potentiometer, enabling raw measurement values representative of the current position of each actuator to be gathered.
A predetermined target value is stored in memory for each of the predetermined seat configurations accessible by a single actuating device, this predetermined target value being equal to the raw measurement value sensed when the seat element is in the desired target position.
Accordingly, to move a seat element towards a predetermined position, the actuator is operated until the current raw measurement value provided by the transducer is equal to the predetermined target value corresponding to the intended position of the actuator and hence the corresponding seat element.
Furthermore, in order to prevent a moveable element of the seat from encountering an obstacle, a known approach is to track the position of this moveable element and prevent the raw measurement value provided by the transducer from exceeding a predetermined threshold value. If the raw measurement value provided by the transducer is equal to this predetermined threshold value, a command to stop the actuator is automatically issued, independently of the control operated by the passenger.
In practice, it has been found that, because of manufacturing tolerances in actuators and mechanical and electronic inaccuracies in transducers, identical actuators do not all provide the same raw measurement value for a same actuator position.
Consequently, when a faulty actuator is replaced by a new actuator, the seat has to be re-programmed, otherwise the response of the seat to a user operation may not be satisfactory owing to the tolerances and inaccuracies of the actuator.
The object of the invention is to propose an actuator for a seat element, which will enable the actuator to be readily replaced with another, without any malfunctions of the seat occurring.
To this end, the invention relates to an actuator for a seat element of the type outlined above, characterised in that it has means for correcting said raw measurement value, said correction means being suitable for defining a correction algorithm which is specific to said actuator and which is suitable for providing a corrected value for the current position of the actuator on the basis of said raw measurement value, and in that said correction means are specific to said actuator and are integrated therein.
Depending on the embodiment, the actuator may incorporate one or more of the following features:
said correction means have a correction unit specific to said actuator and integrated in said actuator, said correction unit having means for storing said correction algorithm when the actuator is manufactured and a data processing unit suitable for providing said corrected value by implementing the stored correction algorithm on the basis of said raw measurement value;
said correction means have means for storing parameters for defining said correction algorithm and means for transmitting said defining parameters to a control unit of the actuator capable of implementing the correction algorithm on the basis of said defining parameters;
the actuator is isolated from a seat before being mounted on the seat;
said correction algorithm depends solely on the structural characteristics specific to said actuator and is independent of the structure of the seat for which it is intended; and
said correction algorithm is suitable for calculating the corrected value as the image of the raw measurement value by means of an affine correction function.
The invention further relates to an actuating system characterised in that it has at least one actuator as defined above and a control unit for the or each actuator, which control unit is linked to the or each actuator so as to receive from the or each actuator the raw measurement value and said defining parameters of the algorithm, and in that the control unit has a data processing unit suitable for providing said corrected value on the basis of said raw measurement value by implementing the correction algorithm on the basis of said received parameters defining the algorithm.
The invention further relates to a family of actuators comprising several actuators as defined above and the correction algorithm of each actuator is such that, for at least one predetermined relative position of the control element by reference to the body, said corrected values provided by all the actuators of the family are equal to a same predetermined value.
Depending on the embodiments:
the correction algorithm of each actuator is such that, for at least two predetermined relative positions of the control element by reference to the body, said corrected values provided by all the actuators of the family are equal to a same predetermined value;
the correction algorithm specific to each actuator is such that the discrepancy between the corrected values provided by the actuators of the family for any set of identical positions of the actuators is smaller than the discrepancy between the raw measurement values provided by the transducers of the same actuators for the same set of identical positions of the actuators.
Finally, the invention relates to a method of manufacturing an actuator intended to be mounted in a seat, the actuator comprising, on the one hand, a body and a control element which can be moved relative to the body, under the control of an actuating motor, and, on the other hand, a transducer disposed between the body and the control element, said transducer being suitable for providing a raw measurement value representative of the current position of the control element relative to the body, characterised in that means for correcting said raw measurement value are integrated in the actuator, said correction means being suitable for defining a correction algorithm which is specific to said actuator and which is suitable for providing a corrected value for the current position of the actuator on the basis of said raw measurement value, and in that it includes a phase during which the correction algorithm defined by said correction means is customised for the specific actuator before the actuator is mounted on the seat.
In particular, said phase of customising the correction algorithm includes the steps of:
positioning the control element relative to the body in at least one predetermined position;
reading the raw measurement value provided by the transducer for the or each predetermined position; and
determining the correction algorithm on the basis of the or each raw measurement value read.